a. Field of the Invention
The present invention generally pertains to wireless communication technology and more specifically to A/D sampling of baseband signals with blocker signals present from adjacent channels.
b. Description of the Background
In wireless communications, such as wireless cell phone communications, different frequency channels are assigned for wirelessly communicating between base stations and transceivers such as cell stations and cell phones. Very often, signals from other cell phones on adjacent channels or other signals (i.e., collectively referred to as blocker or jammer signals) are detected by the transceivers. To avoid this problem, expensive surface acoustic wave (SAW) filters are typically inserted between the IF stage and the baseband stage of the cell phone receiver. SAW filters work very effectively as band-pass filters by only passing the particular frequency channel desired. However, SAW filters are expensive, are implemented as separate discrete components, and as such, occupy valuable room on the printed circuit board of the cell phone. Additionally, separate pin-outs have to be employed for the SAW filters to provide the filtering function between the IF stage and the baseband stage of the receiver. Hence, discrete components such as SAW filters do not provide for a high degree of integration which is an important feature in wireless transceivers. Replacement of the SAW filter with other types of filters, such as active filters, may not provide the channelization that the SAW filter provides and results in larger power consumption. The amount of power consumption in battery-operated transceivers is a critical factor in the design of these devices. Active filters that are constantly-on require power which must be conserved in battery-operated communication devices such as cell phones.
Hence, a technique is needed for providing a sampling circuit that can operate effectively in the presence of blocker or jammer signals in battery-operated mobile communication devices that conserves power and can be integrated into a sampling circuit chip, thereby eliminating the need for off-chip discrete components.